Sexual Reproduction in Flowering Plants
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Questions and Answers

What is the outermost layer of a microsporangium?

  • Tapetum
  • Endothecium
  • Middle layers
  • Epidermis (correct)

    • What is the function of the tapetum?

  • Protection of the developing pollen grains
  • Dehiscence of the anther
  • Nourishment of the developing pollen grains (correct)
  • Formation of the microspore mother cells

    • What is the term for the process of forming microspores from a pollen mother cell?

  • Meiosis
  • Gametogenesis
  • Pollination
  • Microsporogenesis (correct)

    • What is a microspore tetrad?

    <p>Four microspores formed from a single microspore mother cell (A)</p> Signup and view all the answers

    Which cell within a pollen grain is responsible for producing male gametes?

    <p>Generative cell (C)</p> Signup and view all the answers

    Which layer of the pollen grain wall is the outer layer?

    <p>Exine (B)</p> Signup and view all the answers

    What is the significance of the large central vacuole formed in a microspore?

    <p>It displaces the nucleus to the periphery (C)</p> Signup and view all the answers

    At what stage are the pollen grains shed in 60% of angiosperms?

    <p>Two-celled stage (C)</p> Signup and view all the answers

    Which of the following statements accurately describes the micropylar end of an ovule?

    <p>It is the site where the pollen tube enters the ovule. (B)</p> Signup and view all the answers

    How many megaspores are formed from a single megaspore mother cell (MMC) after meiosis?

    <p>Four (B)</p> Signup and view all the answers

    Which of the following is NOT a characteristic of autogamy?

    <p>It can lead to genetic variation in the progeny. (B)</p> Signup and view all the answers

    What is the main difference between chasmogamy and cleistogamy?

    <p>Chasmogamy occurs in flowers that open, while cleistogamy occurs in flowers that remain closed. (C)</p> Signup and view all the answers

    During the development of the embryo sac, how many nuclei are present at the four-nucleate stage?

    <p>Four (A)</p> Signup and view all the answers

    Which of the following structures in the embryo sac is located at the chalazal end?

    <p>Antipodal cells (D)</p> Signup and view all the answers

    What is the difference between geitonogamy and autogamy?

    <p>Geitonogamy requires pollinating agents, while autogamy does not. (A)</p> Signup and view all the answers

    What is the significance of the functional megaspore in megasporogenesis?

    <p>It is the only megaspore that survives and develops into the female gametophyte. (A)</p> Signup and view all the answers

    What is the undifferentiated sheath that covers the root cap of a monocotyledonous embryo?

    <p>Coleorihiza (C)</p> Signup and view all the answers

    What is the residual persistent nucellus in black pepper known as?

    <p>Perisperm (B)</p> Signup and view all the answers

    Which of the following structures is present at the micropylar tip of the synergids in an embryo sac?

    <p>Synergids (A)</p> Signup and view all the answers

    What is the outer layer of a maize grain called?

    <p>Pericarp (A)</p> Signup and view all the answers

    What is the function of the tapetum in a flowering plant?

    <p>To nourish the developing pollen grains (C)</p> Signup and view all the answers

    Which of the following structures is present in a male gametophyte of an angiosperm and helps in the formation of the pollen tube?

    <p>Germ pore (C)</p> Signup and view all the answers

    Which of the following plants would require emasculation and bagging for artificial hybridization?

    <p>Papaya (D)</p> Signup and view all the answers

    What is the process of syngamy?

    <p>Fusion of the egg cell with the male gamete (C)</p> Signup and view all the answers

    What does xenogamy refer to?

    <p>Transfer of pollen from the anther of one plant to the stigma of another plant of the same species. (D)</p> Signup and view all the answers

    What is one characteristic of anemophilous flowers?

    <p>They are odorless and nectarless. (D)</p> Signup and view all the answers

    Which pollination mode relies on insects?

    <p>Entomophily (D)</p> Signup and view all the answers

    What type of flowers do seagrasses primarily use for pollination?

    <p>Flowers that are submerged and release pollen in water. (C)</p> Signup and view all the answers

    What feature characterizes the stigmas of hydrophilous flowers?

    <p>They are long and sticky. (D)</p> Signup and view all the answers

    Which insect is NOT commonly recognized as a pollinator in entomophily?

    <p>Rats (D)</p> Signup and view all the answers

    Which reward is typically provided by entomophilous flowers to attract pollinators?

    <p>Nectar and pollen grains (D)</p> Signup and view all the answers

    What adaptation do anemophilous flowers have to assist with pollen dispersal?

    <p>Small and lightweight floral structures. (D)</p> Signup and view all the answers

    What role does dormancy play for seeds from a farmer's perspective?

    <p>Enables storage of seeds without risk of spoilage. (C)</p> Signup and view all the answers

    Which statement correctly describes the difference between parthenocarpy and apomixis?

    <p>Parthenocarpy involves fertilization, while apomixis does not. (B)</p> Signup and view all the answers

    What is the composition of the exine in pollen grains, and why is it beneficial?

    <p>Sporopollenin, which provides resistance to degradation. (C)</p> Signup and view all the answers

    Which aspect is crucial for understanding the reproductive cycle of angiosperms?

    <p>Both syngamy and meiosis are vital for genetic diversity. (C)</p> Signup and view all the answers

    Why do angiosperms with unisexual flowers exhibit monoecious or dioecious characteristics?

    <p>They have distinct male and female plants. (B)</p> Signup and view all the answers

    Which event is critical after pollination in angiosperms for the successful development of seeds?

    <p>Fertilization and subsequent development. (A)</p> Signup and view all the answers

    In what scenario would farmers prefer using apomictic seeds?

    <p>To maintain uniformity in crop traits over generations. (B)</p> Signup and view all the answers

    What is a characteristic feature of albuminous seeds in angiosperms?

    <p>They have an extensive endosperm that stores nutrients. (D)</p> Signup and view all the answers

    What is the hilum in a typical angiospermic ovule?

    <p>The junction between the body of the ovule and the funicle (B)</p> Signup and view all the answers

    Which of the following terms describes the state of an embryo entering inactivity as the seed matures?

    <p>Dormancy (B)</p> Signup and view all the answers

    What is the ploidy of an apomictic embryo developing from the integument cells?

    <p>2n (A)</p> Signup and view all the answers

    What is the ploidy of an apomictic embryo developing from the megaspore mother cell without reduction division?

    <p>2n (C)</p> Signup and view all the answers

    In a mature embryo sac, what is the function of the synergids?

    <p>They guide the pollen tube towards the egg cell (B)</p> Signup and view all the answers

    What does the term "cleistogamous" refer to?

    <p>Flowers that are closed and self-pollinated (D)</p> Signup and view all the answers

    What is the difference between chasmogamous and cleistogamous flowers?

    <p>Chasmogamous flowers are cross-pollinated, while cleistogamous flowers are self-pollinated. (A)</p> Signup and view all the answers

    What is the main advantage of cleistogamous flowers?

    <p>They can produce seeds even in unfavorable conditions. (C)</p> Signup and view all the answers

    Study Notes

    Sexual Reproduction in Flowering Plants

    • Flowering plants (angiosperms) reproduce sexually
    • Flowers are the sites of sexual reproduction
    • Flowers are specialized reproductive shoots. They have a receptacle with necessary parts.
    • Flower parts play roles in functions such as pollination and dispersal of fruits and seeds
    • Calyx: outermost whorl; individual parts are sepals; protects other floral parts in bud stage
    • Corolla: second whorl; individual parts are petals; attract pollinators; often colorful and fragrant
    • Androecium: third whorl; individual parts are stamens; contain anthers and filaments; produce male gametes
    • Gynoecium/Pistil/Carpel: female reproductive organ; contains stigma, style, and ovary; receives pollen, and develops ovules

    Stamen (Male Reproductive Unit)

    • Stamen is the male reproductive unit of angiosperms (flowering plants)
    • Composed of a filament and an anther
    • Filament is a long, slender stalk
    • Anther is at the top and bilobed (two lobes).
    • Each lobe contains two microsporangia (pollen sacs). Each anther develops into four microsporangia.

    Function of Microsporangia

    • Develop into pollen sacs; extend through the length of the anther
    • Microsporangia develop into pollen sacs
    • Microsporangia contain microspore mother cells.

    Microsporogenesis

    • Microsporangia contains microspore mother cells
    • Each microspore mother cell undergoes meiosis forming four haploid microspores
    • The four microspores are usually arranged in groups of four (tetrads)

    Pollen Grain Development

    • Pollen grains are shed at the 2-celled stage in 60% of angiosperms
    • Pollen grain has a prominent two layered wall: exine and intine
    • Exine is hard and made of sporopollenin; it has unique structure for each species
    • Intine is thin and made of cellulose and pectin
    • Pollen grains have germ pores; sites for pollen tube emergence

    Pollination

    • Pollination is the transfer of pollen grains from anther to stigma of a pistil
    • Types of pollination based on pollinating agents:
      • Anemophily (wind pollination)
      • Entomophily (insect pollination)
      • Hydrophily (water pollination)

    Gynoecium (Female Reproductive Unit)

    • Gynoecium/Pistil/Carpel is the female reproductive unit
    • Composed of Stigma, Style, and Ovary (distinct parts)
    • Stigma is the receptive tip for pollen grains
    • Style is the stalk that connects the stigma to the ovary
    • Ovary is the base where one or more ovules are present.
    • Ovule develops into a seed.

    Structure of an Ovule/Megasporangium

    • Parts of an ovule include:
      • Funicle: stalk that connects the ovule to the placenta
      • Hilum: connection/scar on the ovule where the stalk (funicle) attaches.
      • Integuments:protective layers around the ovule
      • Micropyle: opening in the integuments

    Megasporogenesis

    • Megasporogenesis begins in the nucellus of the ovule
    • The megaspore mother cell undergoes meiosis forming four megaspores.
    • One megaspore survives; remains inside the ovule and develops into embryo sac (female gametophyte)

    Embryo Sac Development

    • The functional megaspore then undergoes repeated mitosis producing several nuclei
    • Eight nuclei are positioned in a characteristic manner in the embryo sac, forming 7 cells in the mature embryo sac

    Double Fertilization

    • Two male gametes reach the embryo sac inside the ovule:
      • One fuses with the egg cell (syngamy)—forming a diploid zygote.
      • The other fuses with two polar nuclei (triple fusion)—forming a triploid primary endosperm cell.

    Post-Fertilization

    • Endosperm accumulates food reserves in the ovule
    • The embryo develop inside the ovule.
    • The ovule develops into a seed.
    • The ovary develops into a fruit which protects the seed/seeds

    Seed

    • A seed contains a seed coat (testa), cotyledons, and the embryo
    • Seed coat protects the seed
    • Cotyledons store food.
    • Seed develop further into a seedling.

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    Class XII Chapter 2 - Sexual Reproduction in Flowering Plants PDF

    Description

    Explore the fascinating process of sexual reproduction in flowering plants, focusing on their specialized structures. Learn about the roles of flowers, their parts, and the functions they serve in pollination and fruit development. This quiz delves into the anatomy of stamen and the function of male and female reproductive organs.

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